intercostal

from The American Heritage® Dictionary of the English Language, 5th Edition.

• adjective Located or occurring between the ribs.
• noun A space, muscle, or part situated between the ribs.

from The Century Dictionary.

• Situated or intervening between successive ribs of the same side of the body: as, intercostal muscles, vessels, spaces.
• noun An intercostal structure, as an artery, and especially a muscle; an intercostalis.
• In iron ship-building, noting a structural member composed of a number of short pieces fitted in the spaces between a series of other continuous structural members which it crosses: as, an intercostal floorplate, one in which the floor is in short pieces between the longitudinals; an intercostal keelson, intercostal longitudinal, one in short pieces between the frames; an intercostal angle-bar, intercostal seam-strap, one in short pieces between frames or deck-beams, etc.

from the GNU version of the Collaborative International Dictionary of English.

• adjective (Anat. & Physiol.) Between the ribs; pertaining to, or produced by, the parts between the ribs.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• adjective anatomy Between the ribs of an animal or person.
• adjective nautical Between the ribs of a boat.
• noun anatomy The intercostal muscles.
• noun anatomy Something that is between the ribs of an animal.
• noun nautical Hull reinforcing inserted between frames or bulkheads of a boat.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun muscles between the ribs; they contract during inspiration
• adjective located or occurring between the ribs